1. Field of the Invention
This invention relates to the field of rechargeable battery systems, and particularly to rechargeable battery systems for portable computers.
2. Description of the Related Art
Many electronic products include rechargeable batteries which enable them to operate without connection to an AC power source. The status of the battery is often of critical importance to the product's user, as the product can operate only as long as the battery retains some useful life. For example, portable computers, such as notebook or laptop computers which are powered by a removable battery pack when not connected to an AC power source, typically provide a battery status screen to a user which might include data related to charge level, product aging, and an estimation of the remaining life for the battery housed within the pack.
Some recent portable computers have embedded a microprocessor, microcontroller, or complex finite state machine (FSM) inside the battery pack. Using this device in combination with a number of sensors and other electronics, voltage, temperature, current and various other variables are measured and processed with circuitry housed within the battery pack itself. Such battery packs are referred to as “Smart Batteries”; communication with the host computer is through an SMBus bus interface using function calls that adhere to the industry standard Smart Battery Data Specification (SBDS).
This results in a very complex and expensive battery pack. The circuitry required to implement a Smart Battery makes up a major part of the pack's electronics, which in turn make up a significant portion of the total cost of the battery pack. The battery pack industry is under continuous pressure to reduce the cost of their products. However, cost reduction is difficult with battery packs configured as described above.